Generally, an automobile is equipped with a burglar alarm to prevent intrusion by a burglar. Both active and passive type burglar alarms have the following defects:
(1) The burglar alarm must be turned on when the user is going to leave his car, but it may be left off due to user negligence, negating its function;
(2) No provision exists for testing the functioning of the alarm and its circuits;
(3) The user has to quickly leave the car after turning off the alarm since the time delay is very short; and
(4) The user may prefer not to test the alarm since it is very noisy.
The inventor applied for a patent for the invention "Burglar Alarm with Re-entry Feature" on March 29, 1983 Ser. No. 480,124). On Sept. 24, 1985, U.S. Pat. No. 4,543,568 was issued by the U.S. Patent Office. The said invention is characterized by the installation of sensors in the doors, hood, and trunk of a car. An exit delay period will begin when the last door is closed. Within this time period the alarm may be temporarily disarmed by again opening a door or the hood or trunk. Simultaneous with the closing of the last door a "chirp" will sound to inform the user that the doors have been properly closed, the alarm is functioning properly, and the exit delay period has begun. Once the exit delay period has expired, the alarm will be triggered by opening a door, hood, or trunk. Such an alarm increases the user's feeling of security, and is very convenient to use.
Currently, many automobile burglar alarms are operated by radio frequency, i.e., a radio frequency transmitter transmits a certain signal to disarm the alarm. A defect of most RF disarming devices is that an armed burglar alarm may be disarmed by external radio frequency signals and thus lose its intended protective function. The present invention eliminates these defects, and can rearm an alarm automatically as well as disarm an alarm in two steps.